In this project I will explain how I made my awesome sounding mini headphone amp that can be powered by a battery or a 9V adapter. You could power it by USB aswell, since I use a specialized power supply circuit that boosts any voltage (as long as it is large enough) to +12V and -12V. This is so that the amplifier can output a truly analog signal at full power, which makes is sound great! You could also use 9V and 0V instead of 12V an -12V, but I have not tested it but it should work.
This project consists of 3 main parts.
1. The power supply (Optional but recommended)
2. The amplifier circuit
3. Assembling and making the housing
Things that need to be improved :
Add a bass & treble control becouse there is a bit too much bass in my opinion.
Side notes :
I know the power supply is overkill, but I think it's a nice addition. It makes you able to power it from nearly any voltage, and keeps the supply voltage for the amplifier at a steady level, as the battery voltage drops.
Feel free to correct me on any mistakes, or suggest improvements. We're all here to learn.
Step 1: What Do You Need?
- Copper clad circuit board for etching, or any prototyping PCB you wish to use
- ABS or Metal box to put everything in
- Flexible copper wire
- Soldering iron and tin
- A drill and some drillbits (To make holes for the potentiometers and audio jacks)
- a simple power switch (I used this type of switch)
- 2 stereo audio jacks, I used 2 6.35mm jacks since my headphones have a 6.35mm jack. This is your personal choice.
Power supply :
2x MC34063 - A very common IC used to boost and reduce voltages, you can find this at practically any electronics store
2x 100uF Electrolytic capacitor - Minimum rating of 25V recommended
2x 470uF Electrolytic capacitor - Minimum rating of 25V recommended
2x 470pF ceramic capacitor - If you hear a high squeeling noise out of the amp, try lowering this value (GOING LOWER THAN 100pF IS NOT RECOMMENDED)
2x 1N5817 or 1N1518 or 1N1519 Schottky Diode - Any rectifier diode will work aswell, but schottky diodes are the most efficient, which is nice to have since we are using batteries.
2x 100uH Inductor - I used a power inductor (the kind where you can see the copper wire wound around a ferrite core)
Resistors - You need two 0.4 Ohm resistors (anything arround that value will do), other resistors are common values, see circuit for all the needed resistors.
A 9V battery clip - To attach the battery to the circuit
1x NE5532 Op-amp - A very nice sounding amplifier IC, it has 2 amplifiers in one chip. Which is handy becouse we are driving each channel (stereo) on a different amplifier.
1x 220k Potentiometer - This does not need to be exactly 220k, you can use any value you have but I don't recommend going under 100k. Try to experiment and see if your pot works. (Feel free to share your results!)
2x 150pF ceramic capacitor - Higher values means your amplifier will respond more to higher frequencies, I don't recommend picking a lower value since it will cause high pitched noise (Which you do not want, trust me)
2x 10uF electrolytic capacitor - Recommended rating of 25V
A variety of resistors - See schematic for all the values
Step 2: The Power Supply
Wiring will be discussed in the last step!
First, we will start by creating the power supply
I have attached the circuit I drew in Proteus as pdf and as an image.
I etched the circuit on a copper clad board (see images) by printing out the PCB layout on a normal printer, marking the holes on the board and then drawing the circuit with permament marker. I then etched the board using hydrochloric acid and hydrogen peroxide. If you want to learn how to etch boards, I suggest you google it. Explaining etching would be too much for this instructable
I have attached a pdf with the MIRRORED PCB traces, it needs to be mirrored since it is going to be on the underside of the board, see picture to know where components go.
You can build this just as well on veroboard or any other prototyping board.
Make sure you connect the IN+ and IN- connections together, if you're using one battery!
You can use 2 batteries, 1 for negative and one for the positive but it's not recommended
Step 3: The Amplifier
Wiring will be discussed in the last step!
The amplifier circuit board was made in the same exact way as the power supply.
again, i added in all the files you need to build the circuit and etch it if you wish to do so.
Feel free to ask any question in the comments, i wil try to answer it as fast as possible.
Step 4: Creating a Housing
For the housing, it's comepletely up to you. Make sure you buy a box that is sufficiently large to fit all your boards.
I used a black ABS box that's about 150x80x50milimeters.You'll have to drill the holes required for a :
- Power switch
- Input jack
- Output jack
- Gain potentiometer (volume)
Step 5: Finally, the Wiring
I created 2 wiring diagrams in paint, since it would be very messy using just a single diagram.
One diagram covers the power, the other one covers the signals.
Notice how the input has only 1 channel, guitars have mono output, so you only connect the tip of the jack. If anyone wants me to make a version to use a stereo input, send me a personal message and i will consider making it (small adjustments). If you're advanced, i'm sure you can figure it out yourself.
I hope it's understandable, if not feel free to leave a comment